During certain interventional procedures that require vascular access, the patient is catheterized through a vein or artery and a catheter is routed to the heart or other region of the cardiovascular system. The initial steps involve placement of a hollow tube within the blood vessel. The hollow tube can be a sheath or catheter. In many cases, these catheters or sheaths are fairly long. Catheters or other devices are routinely routed through these sheaths into the arterial side of the circulatory system where pulsatile blood pressure generally averages 100 mm Hg cycles and pulses at an average rate of approximately 1 to 3 beats per second. The peak systolic pressures in the arterial side in a normal patient are around 110 to 130 mm Hg and the lowest diastolic pressures are around 70 to 90 mm Hg. In a hypertensive patient experiencing what is known as high blood pressure, the peak systolic arterial pressure can exceed 250 mm Hg. A catheterization lab or operating room is typically a clean room, which is maintained at positive pressure ranging from 0 to 2 mm Hg. When a catheter is routed into the arterial system, the distal end of a through lumen will be exposed to these arterial blood pressures and a positive pressure gradient will exist between the distal end and the proximal end of the catheter can be such that, unless proper hemostasis is maintained, blood is forced out through the catheter into the ambient environment.
There are an increasing number of cases where a sheath is routed to the venous side. Its distal end is exposed to central venous blood pressure, which cycles at the same rate as the arterial side, approximately 1 to 3 beats per second. The normal, healthy, pulsatile venous pressures are lower than those in the arterial side and can range between low values of around 3 to 5 mm Hg and peak values of around 15 to 20 mm Hg with an average of approximately 10 mm Hg. Patients with ectopic beats or premature ventricular contractions can achieve nearly zero central venous pressure during part of the cardiac cycle. Patients with tricuspid incompetence and conduction pathologies can experience right atrial pressures of −5 to −10 mm Hg. In the central venous circulation, for example, as measured in the right atrium of the heart, the distal end of the sheath can be exposed, during part or all of the cardiac cycle, to pressures equal to or below those to which the proximal end of the sheath is exposed. When the room or ambient pressure, to which the proximal end of the sheath is exposed, is above that of the distal end of the sheath, a negative pressure gradient or pressure drop can occur. Such a negative pressure drop allows air to be forced into the proximal end of the catheter. Should the air reach the distal end of the catheter by way of a through lumen, it could escape into the blood stream in the form of large or small bubbles, resulting an air embolism. Such air embolisms can cause harm to the health of the patient, or even death, and need to be avoided. This situation can be exacerbated by ambient room pressures often found in the cath lab. Under normal conditions, the environment of the clean room, operating theatre, or catheterization lab can be maintained at an elevated air pressure of around 5 to 10 mm Hg above exterior air pressure. Thus, a right atrial pressure, which momentarily dips to 2 mm Hg, can be overcome by a room air pressure of 2 to 3 mm Hg causing air to be forced retrograde through the catheter and into the circulatory system.
Typical arterial catheter procedures include percutaneous transluminal coronary angioplasty, coronary stenting, aortic stent-graft procedures, endarterectomy, and the like. In the United States, more than 500,000 of these arterial procedures are performed each year. The number of venous procedures being performed each year is increasing as more endovascular therapies evolve or are developed for pathologies such as atrial fibrillation, mitral valve repair, mitral valve replacement, and the like. There are currently more than 200,000 electrophysiology procedures performed in the right and left atrium of the heart annually in the United States. During a venous procedure, a catheter is routed through the venous circulation where low instantaneous, or pulsatile, pressures can occur. During the approach to the heart and in preparation for a trans-septal puncture, the distal end of the catheter can reside in the vena cava or right atrium for a substantial amount of time. Such positioning renders the catheter at risk for being exposed to a negative pressure drop and the potentially catastrophic consequences of retrograde air flow. An air embolism or bubble escaping into the venous circulation can lodge in the lungs causing a pulmonary embolism. Pressures in the left atrium are similar to those in the right atrium. Left atrial pressure is pulsatile and can have peak values of around 10 to 20 mm Hg and minimum values of between −5 and 5 mm Hg. Negative minimum pressures are experienced in patients with certain pathophysiologies such as aortic stenosis. These types of patients are often the ones who undergo catheterization procedures. Left sided (arterial) procedures, which are accessed from the right (or venous) side present a further complication in that a gas bubble or embolism that escapes into the arterial side can be pumped by the heart to sensitive tissues where it can lodge, prevent distal blood flow, and thus cause ischemia. Such ischemia is potentially life threatening if it occurs in the cerebrovasculature or the coronary arteries.
Current devices and methods prevent air entrainment into a sheath or catheter or for preventing blood escape from these sheaths or catheters involve the use of valves such as stopcocks, hemostasis valves, adjustable Tuohy-Borst valves, and the like. These devices are adequate at preventing the loss of substantial amounts of blood during arterial procedures. The current devices, however, are less well suited to preventing air backflow into the sheath or catheter and possibly into the patient. Instances can arise where a hemostasis valve breaks or becomes disconnected from the sheath or catheter and a substantial bolus of air can enter the cardiovascular system with sometimes catastrophic consequences. Even without such equipment failure, operator error can result in air being pumped retrograde into the blood stream by ambient air pressure, if a Tuohy-Borst valve is not properly adjusted, a hemostasis valve becomes distorted, or too small a catheter is used for the type of hemostasis valve.
There is a need for improved systems, devices, apparatus and methods for preventing air entrainment into a patient through catheters routed into the venous circulation. Such systems, devices, apparatus, and methods need to accept catheters or instrumentation through their central lumens and close the seal around those catheters better than current devices. The systems further need to close more quickly than the current systems when the inserted catheter is removed. The current systems need also to be improved to prevent air passage retrograde back into the catheter while still maintaining device operability.